Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Nov. 05, 2018
Document And Entity Information [Abstract]
Entity Registrant Name	LGL GROUP INC
Entity Central Index Key	0000061004
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		4,824,662
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q3
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Entity Small Business	true
Entity Emerging Growth Company	false